The present invention relates to a method for subjecting a natural cellulose-type textile product or a natural cellulose-containing textile product to pretreatment, i.e., to desizing, scouring and bleaching under wet-heat.
For the rationalization of the pretreatment of natural cellulose-type textile products in recent years, it is required to spare energy and resources such as the treating agent and manpower, to simplify the treating process and to speed up the treatment. For elevating the quality of the product, on the other hand, a high pressure steamer has been developed to treat a textile product continuously under wet-heat at high temperature and pressure by using a high pressure steamer.
The standard process for desizing, scouring and bleaching a textile by utilizing a conventional high pressure steamer is a two-bath two-stage method, in which a textile product to be treated is soaked with a treating solution containing 60 to 100 g/l of caustic soda, 10 to 20 g/l of an oxidative desizing agent and 10 to 15 g/l of a scouring agent at the ordinary temperature steamed for 60 seconds in a saturated water vapor atmosphere at a temperature from 130.degree. to 150.degree. C. under pressure, cooled and washed well, soaked with an aqueous alkaline hydrogen peroxide solution at pH 11-12 containing 40 to 80 cc/l of 35% hydrogen peroxide, 5 g/l of caustic soda, 10 g/l of a hydrogen peroxide stabilizer and a metal ion sequestering agent at the ordinary temperature, and then steamed again for 60 seconds in a saturated water vapor atmosphere at a temperature from 120.degree. to 125.degree. C. On the other hand, the general procedure for a one-bath one-stage method comprises applying an aqueous strongly alkaline hydrogen peroxide solution containing 10 to 30 g/l of caustic soda, 10 to 20 g/l of an oxidative desizing agent, 40 to 70 g/l of 35% hydrogen peroxide, 10 to 20 g/l of a scouring agent, 10 g/l of a hydrogen peroxide stabilizer and 5 g/l of a metal ion sequestering agent, and steaming the textile product in a saturated water vapor atmosphere at 130.degree. to 140.degree. C.
However, in the former case, after the desizing and scouring with the use of caustic soda, oxidative desizing agent and scouring agent and the washing thereof, bleaching must be done with the use of alkaline hydrogen peroxide solution. Thus, the treatment must be done uneconomically in two stages. The latter instance can be done in one stage, but, since caustic soda, oxidative desizing agent and hydrogen peroxide are used in one bath, there is a problem in the pH of the treating solution, and the effects of the treating agents are offset with one another before the agents act on the textile product, causing the wastefullness of the treating agents, deteriorating the treating effecfs on dewaxing, denepping and decolorization, and weakening the strength of the product.